In ubiquitous computing systems, several devices may coordinate to help a user accomplish her tasks. Careful design of device-device and user-device interaction is crucial to protect the user from the complexity of these systems. Proxies that act on the user?s behalf can significantly improve user-device interaction by "invisibly" providing personalization data and collecting information from devices. But correctly associating devices and user proxies is challenging, particularly in highly mobile, multi-person, multi-device environments. Highly accurate association generally requires an explicit action on the user?s part, which distracts them from their task. We present Facile, a software framework for supporting applications that require invisible association. Facile is independent of the physical communication layer and is designed to minimize latency and power consumption. We describe the construction of three applications in Facile, and our work toward integrating Facile with a capacitively-coupled communication mechanism.